Early blight (Alternaria solani)
Leaf spots of early blight are circular, up to 12 mm in diameter, brown, and often show a circular pattern.
On the potato tuber early blight results in surface lesions that appear a little darker than adjacent healthy skin. Lesions are usually slightly sunken, circular or irregular, brown and vary in size up to 1-2 cm in diameter. There is usually a well defined and sometimes slightly raised margin between healthy and diseased tissue. Internally, the tissue shows a brown to black corky, dry rot, usually not more than 6 mm. Deep cracks may form in older lesions.
Early blight thrives best under warm wet conditions.
- Use certified disease-free seeds
- Practise rotation with non-solanaceaous crops.
- Practise good field hygiene. Remove infected leaves during the growing season and discard all badly infected potato plant debris at the end of each season.
- Avoid overhead irrigation and lay down a thick organic mulch to prevent soil splashing onto lower leaves.